背景色を、コンテキスト(文脈)に応じた色にするクラス。
p要素bg-primary
bg-success
bg-info
bg-warning
bg-danger
<p class="bg-primary">bg-primary</p> <p class="bg-success">bg-success</p> <p class="bg-info">bg-info</p> <p class="bg-warning">bg-warning</p> <p class="bg-danger">bg-danger</p>
span要素<span class="bg-primary">bg-primary</span>, <span class="bg-success">bg-success</span>, <span class="bg-info">bg-info</span>, <span class="bg-warning">bg-warning</span>, <span class="bg-danger">bg-danger</span>,
div要素<div class="bg-primary">bg-primary</div> <div class="bg-success">bg-success</div> <div class="bg-info">bg-info</div> <div class="bg-warning">bg-warning</div> <div class="bg-danger">bg-danger</div>